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With an average altitude of 4,500m above sea level, Nagqu in northern Tibet is dubbed "the ridge of the roof of the world". Covering 446,000 sq km, the prefecture accounts for 37 percent of the autonomous region's territory.

Nagqu has the largest pastoral area, and the highest productivity in the region. Breeding livestock accounts for 70 percent of the prefecture's gross domestic product, and more than 90 percent of Nagqu residents make a living at it. It accounts for one-third of the region's animal husbandry.

But a chilly winter with fuel shortages and snowstorms are not the only consequences of global warming in this region. Flooding has also become a major threat.

After the Arctic and Antarctic, the Qinghai-Tibet plateau has the third largest number of glaciers. However, in the past 50 years, 82 percent of the plateau's glaciers have melted. The plateau has lost 10 percent of its permafrost layer in the past decade, according to the Chinese Academy of Sciences.

Yak dung is laid on the mud wall of herder Bugye's house for drying before it is used as fuel in Nagqu prefecture, Tibet autonomous region, on Sept 12. [China Daily]

With the increased snow and glacier melt, the water levels of some 117 lakes in Nagqu alone have been rising. The water level of Tibet's second biggest lake, the Serling Co Lake, has risen 20 cm a year since 1997. At present, its water surface area reaches about 1,620 sq km. Compared with the coverage in 1997, the lake has expanded 5km to the west, 18km to the north, 23km to the southwest and 3km to the south.

Since the 1990s, rising water levels in lakes have submerged 106,667 hectares of pastureland as well as more than 3,000 livestock pens in total. Nearly 1,400 households in Nagqu had to rebuild their homes. More than 1,000 households, or nearly 6,000 people, are still living under the threat of flooding.

"In winter, water seeped into our house and around the stove and froze," said Penpa Tashi from Namarche county in Nagqu. "When summer came and the ice melted, the stink of yak dung filled the house. Because of the flooding, our house might collapse at any time, so we have to move."

Nagqu prefecture deputy chief Gyaltsen Wangdrak has kept a close eye on the weather changes, accumulating data on how much damage the extreme weather fluctuations have caused to both the local economy and the herders over the past decade.

In 2003, Gyaltsen met Lin Erda, a senior researcher of the Chinese Academy of Agricultural Sciences. They pooled together a 1.3 million yuan fund - with 800,000 yuan from Lin and 500,000 from the local Nagqu government - to study the long-term effects of global warming on Nagqu's grasslands.

Over the course of 12 months, they mapped the degradation of grassland in Nagqu with remote sensing technology. The map showed that nearly half of Nagqu's alpine grassland had degraded. The affected area covers about 20 million hectares, with 10 percent, or 4 million hectares, seriously degraded.

Based on this information, the prefecture started two experiments in Amdo county at the foot of Tanggula Mountain to restore seriously degraded grassland through sprinkler irrigation and reseeding. The goal is to quadruple the amount of grass from 600 kg to 2,400 kg per hectare.

The prefecture has also leased from local herders some 33 hectares of healthy grassland and 20 sheep at 15,000 yuan a year to study how much grass an animal needs annually.

Through this research, Gyaltsen and scientists are hoping to come up with more scientific figures on how to raise livestock on alpine grassland.

"It will take many years to complete the experiments," Gyaltsen said. "But we have to persist. All the people living on the plateau face unprecedented changes from global warming. No one knows how to deal with it."

"We have to blaze a trail."

(China Daily October 7, 2008)